The present disclosure relates to systems and methods of plugging a wellbore for abandonment and, more particularly, to using a casing cutting tool having a jetting tool with fluid jet nozzles and a retractable wedge for removing wellbore casing in preparation for the placement of a cement plug.
In the oil and gas industry, once a hydrocarbon bearing well reaches the end of its useful life, the well is decommissioned for abandonment. Regulations under various state and federal laws require decommissioned wells to be properly plugged and sealed using “plug and abandonment” procedures before abandoning the well. Plug and abandonment operations performed in a cased wellbore require that certain portions of the wellbore be filled with cement to prevent the upward movement of fluids toward the surface of the well. To seal the wellbore, a bridge plug is typically placed at a predetermined depth within the wellbore and cement is then introduced to form a column of cement high enough to ensure that the wellbore is permanently plugged.
In addition to simply sealing the interior of the wellbore, state and federal regulations also often require that an area outside of the wellbore be sufficiently blocked to prevent any fluids from migrating towards the surface of the well along the outside of the casing string. For example, in well completions having one or more strings of casing lining the wellbore, the annular area between the strings can form a fluid path even though they had been cemented into place when the well was initially completed. The combination of poor cement sealing and/or weakening conditions of cement over time may additionally lead to fluid paths opening in the cement that could allow for the passage of fluid to the surface.
In order to ensure the area outside of the wellbore is adequately blocked, cement is typically injected or “squeezed” through perforations in the casing and into the formation surrounding the wellbore. By pumping cement in a non-circulating system, a predetermined amount of cement may be forced into the surrounding formation and can thereafter cure to form a fluid barrier. In cases where the wellbore to be plugged and abandoned has an outer string of casing and an inner string of casing coaxially disposed therein, the annular space between the concentric strings must also be squeezed with cement to prevent the subsequent migration of fluid towards the surface of the well.
The cement squeeze approach, however, does not guarantee that the cement fully contacts the surrounding formation because the cement is typically required to pass through a narrow passage that may or may not allow the cement to reach all areas of the surrounding formation. Accidental over-pressurization may also create a fracture, which may result in a failed plugging operation. As a result, the plug job may be compromised or rendered at least partially ineffective. Another approach that exposes the surrounding rock formation is reaming out the wellbore over the desired area. Reaming, however, is quite time consuming and costly and therefore not a viable alternative in some wells.